Biparatopic protein constructs that are directed against IL-23, and in particular against the p19 subunit of IL-23. The constructs comprise at least a first binding domain or binding unit directed against a first defined epitope on p19 and at least a second binding domain or binding unit directed against a second defined epitope on p19 (or the p19/p40 interface). The binding domains or binding units may in particular be a domain antibody, a single domain antibody, a dAb or a Nanobody®. The constructs and pharmaceutical compositions comprising the same can be used for the prevention and/or treatment of diseases and disorders associated with IL-23 or IL-23 mediated signaling, such as inflammation and inflammatory disorders such as colitis, Crohn's disease and IBD, infectious diseases, psoriasis, cancer, autoimmune diseases, sarcoidosis, transplant rejection, cystic Fibrosis, asthma, chronic obstructive pulmonary disease, rheumatoid arthritis, viral infection, and common variable immunodeficiency.